Display apparatus and method of manufacturing optical sheet for the same

ABSTRACT

A display apparatus includes a display panel and a backlight unit for an embodiment. The display panel includes a plurality of pixels and the backlight unit supplies light to the display panel. The backlight unit includes a light source, which generates the light, and an optical sheet. The optical sheet includes a plurality of prism patterns formed on a surface of the optical sheet facing the display panel. The prism patterns include a plurality of peaks and a plurality of valleys to change the path of the light, and a plurality of diffusion patterns arranged at the peaks and valleys.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to Korean PatentApplication No. 2008-93775 filed on Sep. 24, 2008, the contents of whichare herein incorporated by reference in their entirety.

BACKGROUND

1. Technical Field

The present invention relates generally to a display apparatus, whichmay have an improved display quality, and a method of manufacturing anoptical sheet for the same.

2. Related Art

Liquid crystal displays (LCD) have become extensively used because oftheir various characteristics, such as light weight, thinness, and lowpower consumption. The typical LCD includes an LCD panel that has twotransparent substrates and liquid crystal cells arranged between the twotransparent substrates in a matrix form, a panel driver that drives theLCD panel, and a backlight unit that supplies light to the LCD panel.

The backlight unit includes a light source that emits the light, a lightguide plate that guides the light from the light source to the liquidcrystal display panel, and optical sheets arranged above the light guideplate. The optical sheets generally include a diffusion sheet, a prismsheet, and a protective sheet. The prism sheet includes a prism patternof which peaks and valleys are alternately disposed. Thus, a moiréphenomenon occurs due to interference of periodic patterns betweenpitches of the peaks and pitches of pixels of the LCD panel.

SUMMARY

One embodiment of the present invention provides a display apparatus,which may have an improved display quality. Another embodiment of thepresent invention provides a method of manufacturing an optical sheetfor the display apparatus.

In an embodiment of the present invention, a display apparatus includesa display panel including a plurality of gate lines, a plurality of datalines crossing the gate lines, a plurality of pixels defined by the gatelines and the data lines, and a backlight unit disposed at a rearportion of the display panel to supply light to the display panel. Thebacklight unit includes a light source generating the light and anoptical sheet. The optical sheet includes a plurality of prism patternshaving a plurality of peaks and a plurality of valleys, the prismpatterns being formed on a first surface of the optical sheet facing thedisplay panel, and a plurality of diffusion patterns arranged at thepeaks and valleys, and which overlap the pixels at a predeterminedinterval.

Each of the pixels includes a red sub-pixel, a green sub-pixel, and ablue sub-pixel, and the red, green, and blue sub-pixels extend in afirst direction and are arranged along a second direction substantiallyperpendicular to the first direction. The prism patterns are arrangedinclined with respect to the gate lines or the data lines at apredetermined angle of about 23 degrees to about 30 degrees. As aspecific example, the angle of inclination of the prism patterns withrespect to the gate lines is about 28 degrees.

Each of the diffusion patterns is spaced apart from adjacent peaksthereto or adjacent valleys thereto by an interval of

$\frac{P}{2\;\cos\;\theta},$where P denotes a pitch of the prism patterns and θ denotes the angle ofinclination, which is not equal to 90 degrees and is not equal to 270degrees. Each of the diffusion patterns, which is arranged along a samepeak of the peaks or a same valley of the valleys, is spaced apart froman adjacent diffusion pattern thereto by an interval of

$\frac{X}{\cos\;\theta},$wherein X denotes a distance between two lines that extend in the firstdirection to respectively bisect two adjacent sub-pixels, and θ denotesthe angle of inclination, which is not equal to 90 degrees and is notequal to 270 degrees. Each of the red, green and blue sub-pixelsoverlaps at least one diffusion pattern of the diffusion patternsarranged at the valley and at least one diffusion pattern of thediffusion patterns arranged at the peak.

In another embodiment of the present invention, a method ofmanufacturing an optical sheet is provided as follows. A base sheet isprepared with a roller applied to a first surface of the base sheet. Theroller includes pressurization portions and decompression portions eachof which extend in an axial direction of the roller, with recessesarranged along the pressurization portions and the decompressionportions in a predetermined interval. The first surface is pressed bythe roller. Then, the base sheet is cured. The recesses of the rollermay be formed by using a laser. The base sheet may be cured byultraviolet rays. In addition, a reflection pattern may further beformed on a second surface opposite to the first surface.

According to the above, the diffusion patterns of the optical sheetoverlap the pixels of the display panel to change the brightness of thelight, so that the periodicity of the brightness pattern is weakened andthe moiré may be reduced. In addition, the base sheet is pressed by theroller on which are the recesses to form the diffusion patterns, so thatthe diffusion pattern may be easily formed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of embodiments of the present inventionwill become readily apparent by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings wherein:

FIG. 1 is an exploded perspective view showing a display apparatusaccording to an embodiment of the present invention;

FIG. 2 is a sectional view showing a display panel and a backlight unitof FIG. 1 according to an embodiment of the present invention;

FIG. 3 is a plan view showing an optical sheet with a display panelaccording to an embodiment of the present invention;

FIGS. 4A to 4D are views showing image inspection patterns used toinspect image quality of the display apparatus of FIG. 1 according to anembodiment of the present invention;

FIGS. 5A to 5D are views showing display panels displaying imagesaccording to the image inspection patterns of FIGS. 4A to 4D,respectively, according to an embodiment of the present invention;

FIG. 6 is a sectional view showing an optical sheet of FIG. 1 accordingto another embodiment of the present invention; and

FIGS. 7A, 7B, 8, and 9 are views illustrating a method of manufacturingan optical sheet of FIG. 1 according to an embodiment of the presentinvention.

DETAILED DESCRIPTION

It will be understood that when an element or layer is referred to asbeing “on”, “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numbers refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, for example, the term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms, “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “includes”and/or “including”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, embodiments of the present invention will be explained indetail with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view showing a display apparatus andFIG. 2 is a sectional view showing a display panel and a backlight unitof FIG. 1 in accordance with one or more embodiments of the presentinvention.

Referring to FIGS. 1 and 2, a display apparatus 50 includes a displaypanel 100 that displays images, a gate driver 210 and a data driver 220that drive the display panel 100, a backlight unit 300 that supplieslight to the display panel 100, and a mold frame 400 that receives thedisplay panel 100 and the backlight unit 300 therein.

The display panel 100 includes a thin film transistor substrate 110, acolor filter substrate 120, and a liquid crystal 130 interposed betweenthe thin film transistor substrate 110 and the color filter substrate120.

The thin film transistor substrate 110 includes a plurality of gatelines 111 extending in a direction, a plurality of data lines 112extending in a direction substantially perpendicular to the gate lines111, a plurality of thin film transistors 115 each of which is connectedto a corresponding gate line and a corresponding data line, and aplurality of pixel electrodes 117 connected to the thin film transistors115, respectively.

The color filter substrate 120 includes a black matrix 121 that coversareas in which images are not displayed, color filters 122 that displayred, green, and blue colors, and a common electrode 128 that forms anelectric field together with the pixel electrodes 117.

The liquid crystal 130 has dielectric anisotropy and is aligned betweenthe thin film transistor substrate 110 and the color filter substrate120. The liquid crystal 130 adjusts the transmittance of light suppliedfrom the backlight unit 300.

The thin film transistor substrate 110 and the color filter substrate120 are coupled with a first polarizing film 131 and a second polarizingfilm 133, respectively. The first polarizing film 131 and the secondpolarizing film 133 polarize light incident thereto. In the presentembodiment, at least one of the first and second polarizing films 131and 133 may be formed with an anti-glare layer (not shown).

The gate driver 210 is formed on the thin film transistor substrate 110by a chip-on-glass scheme. The gate driver 210 applies a gate on/offsignal to the gate lines 111.

The data driver 220 is mounted on a signal transmission film 225 by atape carrier package scheme. The data driver 220 is electricallyconnected to the thin film transistor substrate 110 and a drivingcircuit board 240 through the signal transmission film 225. The datadriver 220 applies pixel data to the transistors 115 connected to thedata lines 112.

The driving circuit board 240 includes a printed circuit board on whicha plurality of signal transmission lines is formed. Various electricparts and a timing controller 230 are mounted on the driving circuitsubstrate 240. The timing controller 230 receives external power sourcevoltage and various signals and applies control signals to the gate anddata drivers 210 and 220 and the pixel data to the data driver 220 todisplay images. In addition, the driving circuit substrate 240 suppliesthe power source voltage to the gate driver 210 and the data driver 220through the signal transmission film 225.

The backlight unit 300 is disposed under the display panel 100 to supplylight to the display panel 100. To this end, the backlight unit 300includes a light source 310, a light guide plate 320, a reflection sheet330, a diffusion sheet 335, and an optical sheet 340.

The light source 310 generates light and supplies the light to thedisplay panel 100. The light source 310 may include light emittingdiodes or lamps. In the present embodiment, in order to reduce thethickness of the display apparatus 50, the light source 310 includeslight emitting diodes. The light source 310 is mounted on a light sourcesubstrate 315 and disposed adjacent to a side portion of the light guideplate 320, so that the light source 310 may supply the light to thelight guide plate 320.

The light source substrate 315 may be a flexible printed circuit board.The light source substrate 315 may be electrically connected to a powersource device (not shown) to apply the power source voltage to the lightsource 310. The light source substrate 315 may be accommodated in themold frame 400.

The light guide plate 320 is disposed such that a side portion thereofis adjacent to the light source 310, and changes paths of the lightincident through the side portion from the light source 310 to allow thelight to travel to the display panel 100. The light guide plate 320 mayinclude acrylic material and may have a dot pattern or a V-shape patternto reflect the light.

The reflection sheet 330 is disposed under the light guide plate 320 andreflects the light leaked downward from the light guide plate 320 to thedisplay panel 100.

The diffusion sheet 335 is disposed on the light guide plate 320 anddiffuses the light exiting from the light guide plate 320 such that thediffused light has a uniform incidence into the display panel 100.

The optical sheet 340 is disposed on the diffusion sheet 335. Theoptical sheet 340 includes a base sheet 345, which includes atransparent polymer material, and a plurality of prism patterns arrangedon a surface of the base sheet 345. The prism patterns 347 change thepaths of the light incident thereto, so that the light travels towardthe display panel 100 in the vertical direction with respect to thedisplay panel 100. In addition, the prism patterns 347 include peaks 350defined by two adjacent surfaces inclined against the base sheet 345 andvalleys 360 defined by two adjacent peaks 350, the peaks 350 and thevalleys 360 being alternately disposed. The optical sheet 340 includesdiffusion patterns 370 arranged on the prism patterns 347 and spacedapart from each other. If the diffusion patterns 370 are arranged on thepeaks 350, the diffusion patterns 370 reduce the collecting efficiencyof the prism patterns 347, and if the diffusion patterns 370 arearranged on the valleys 360, the diffusion patterns 370 improve thecollecting efficiency of the prism patterns 347. The collectingefficiency of the optical sheet 340 varies by the diffusion patterns370, thereby reducing a moiré phenomenon (or moiré effect). If thediffusion patterns 370 are not formed on the optical sheet 340, theoptical sheet 340 may be spaced apart from the display panel 100 inorder to reduce the moiré phenomenon. On the other hand, the opticalsheet 340 including the diffusion patterns 370 may reduce the moiréwithout any influence from the distance between the optical sheet 340and the display panel 100, so that the display panel 100 may be slim.

In order to supply the light to the display panel 100, the backlightunit 300 may be placed adjacent to a side face of the display panel 100(e.g., edge illumination type) or placed under the display panel 100(e.g., direct illumination type). In addition, the backlight unit 300may further include a protection sheet (not shown) disposed on theoptical sheet 340 to protect the optical sheet 340.

The mold frame 400 includes an insulating material such as plastic. Themold frame 400 accommodates the display panel 100 and the backlight unit300 therein to protect the display panel 100 and the backlight unit 300from external impacts.

FIG. 3 is a plan view showing an embodiment of an optical sheet 340 witha display panel 100.

Referring to FIG. 3, the display panel 100 includes a plurality ofpixels 160. Each of the pixels 160 has a substantially rectangular shapeof which one side has a length of about 250 micrometers to about 300micrometers. More particularly, the one side of each pixel 160 may havea length of about 283.5 micrometers. Each of the pixels 160 includesthree sub-pixels 161, 163, and 165 corresponding to red, green, and bluecolors, respectively. For example, each of the pixels 160 may include ared sub-pixel 161, a green sub-pixel 163, and a blue sub-pixel 165. Thesub-pixels 161, 163, and 165 extend in a first direction in which a dataline (not shown) of the display panel 100 extends and are arranged alonga second direction substantially perpendicular to the first direction.

Referring to FIGS. 2 and 3, the optical sheet 340 includes the prismpatterns 347 arranged on its surface facing the display panel 100. Theprism patterns 347 have a pitch P of about 100 micrometers to about 300micrometers. The pitch P is defined by a distance between two adjacentpeaks 350. If the pitch P is about 100 micrometers or below, thecollection efficiency is lowered, and if the pitch P is about 300micrometers or above, the light supplied to the pixels 160 has anonuniform brightness distribution since the pitch P exceeds the size ofthe pixels 160.

The optical sheet 340 is disposed under the display panel 100 andarranged such that the prism patterns 347 are inclined with respect tothe sub-pixels 161, 163, and 165 at a predetermined angle θ (alsoreferred to as “angle of inclination”). As shown in FIG. 3, since theprism patterns 347 are arranged inclined at angle θ with respect to areference line A-A′ extending in the second direction, in which the gateline extends, the moiré effect caused by interference between thearrangement period of the sub-pixels 161, 163, and 165 and the pitch Pof the prism patterns 347 may be prevented. Although not shown in FIG.3, the reference line A-A′ may be chosen to extend in the firstdirection, in which the data line extends. Therefore, the prism patterns347 may be arranged inclined with the gate and data lines of the displaypanel 100 at a predetermined angle. In the present embodiment, astructure for which the reference line A-A′ extends in the seconddirection and the prism patterns 347 are arranged inclined with respectto the reference line A-A′ at the angle θ will be described as anexample.

The moiré effect may be caused by periodicity of the light incident intothe sub-pixels 161, 163, and 165 after passing through the prismpatterns 347. In detail, the sub-pixels 161, 163, and 165 include aline-shaped bright area caused by the light that has passed through thepeaks 350 and a line-shaped dark area caused by the light that haspassed through the valleys 360. The dark area has a brightness lowerthan that of the bright area. When the bright area and the dark area arealternately arranged in the sub-pixels 161, 163, and 165 that areregularly arranged, a wave pattern may be visible due to theperiodicity. If the pitch P of the prism patterns 347 exactly matcheswith the arrangement period of the pixels 160, the moiré pattern may notoccur. This is difficult, however, to realize. In order to avoid suchmoiré effects due to periodicity, the prism patterns 347 are arrangedinclined with respect to the sub-pixels 161, 163, and 165.

The prism patterns 347 are inclined with respect to the reference lineA-A′ at the angle of about 23 degrees to about 30 degrees. Moreparticularly, the prism patterns 347 are inclined with respect to thereference line A-A′ at an angle of about 28 degrees. In the exampleswhere the prism patterns 347 are inclined with respect to the referenceline A-A′ at an angle less than 22 degrees or more than 31 degrees, themoiré effect increases.

Each of the sub-pixels 161, 163, and 165 includes at least one brightarea and at least one dark area since each peak 350 and each valley 360overlap at least one sub-pixel of the sub-pixels 161, 163, and 165.Thus, the diffusion patterns 370 are arranged overlapped with thesub-pixels 161, 163, and 165 to weaken the periodicity by varying thebrightness of the bright and dark areas.

The diffusion patterns 370 are arranged on the prism patterns 347overlapping the sub-pixels 161, 163, and 165 in a predetermined interval(e.g., I1 seen in FIG. 3). For instance, the diffusion patterns 370 maybe arranged on the peaks 350 and the valleys 360 overlapping a centerline that extends in a longitudinal direction of each of the sub-pixels161, 163, and 165 such that the center line bisects each of thesub-pixels 161, 163, and 165. The diffusion patterns 370 are protrudedtoward the display panel 100 to allow each diffusion pattern to have ashape defining a portion of a spherical shape or a portion of an ovalshape when viewed in a sectional view taken along a direction orthogonalto a direction in which the peaks 350 and the valleys 360 extend. Eachof the diffusion patterns 370 has a diameter of about 5 micrometers toabout 50 micrometers. In the present embodiment, the position of thediffusion patterns 370 is not limited to the area overlapping the centerline, and the diffusion patterns 370 may be arranged on the peaks 350and the valleys 360 overlapping the sub-pixels 161, 163, and 165.

The diffusion patterns 370 may be arranged on the peaks 350 and thevalleys 360 according to the predetermined interval (I1). In detail, theinterval (I1), between the diffusion patterns 370 arranged on one peakof the peaks 350 and one valley of the valleys 360 adjacent to the onepeak and extending in the first (data line) direction (or longitudinaldirection of the sub-pixels), is determined by Equation 1 as follows.

$\begin{matrix}{{I\; 1} = \frac{P}{2\;\cos\;\theta}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1, I1 denotes the interval between the diffusion patterns370 arranged on one peak of the peaks 350 and one valley of the valleys360 adjacent to the one peak, P denotes the pitch of the prism patterns347, and θ denotes the angle of inclination (θ is not equal to 90degrees or 270 degrees). Each of the sub-pixels 161, 163, and 165overlaps at least two diffusion patterns 370.

In addition, the diffusion patterns 370 may be arranged on the same peakof the peaks 350 of the prism patterns 347 in a predetermined interval(I2). This interval (I2), between the diffusion patterns 370, isdetermined by Equation 2 according to an interval (X) between the centerlines of two adjacent sub-pixels—for instance, a red sub-pixel 161 and agreen sub-pixel 163—as follows.

$\begin{matrix}{{I\; 2} = \frac{X}{\cos\;\theta}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

In Equation 2, I2 denotes the interval between the diffusion patterns370 arranged on the same peak, X denotes the interval between twoadjacent center lines, and θ denotes the angle of inclination (θ is notequal to 90 degrees or 270 degrees).

FIGS. 4A to 4D are views showing image inspection patterns used toinspect image quality of the display apparatus of FIG. 1, and FIGS. 5Ato 5D are views showing display panels displaying images according tothe image inspection patterns of FIGS. 4A to 4D, respectively, inaccordance with one or more embodiments.

As shown in FIGS. 4A to 4D, various image quality inspection patternshave been applied to the display panel since the moiré phenomenondecreases as a whole in the display apparatus employing the opticalsheet. As a result, the moiré interference has been reduced.

FIGS. 4A, 4B, 4C, and 4D show a white pattern, a dot pattern, a verticalline pattern, and a horizontal line pattern. When the image qualityinspection pattern is provided, the display panel displays an imageusing pixels including red, green, and blue sub-pixels.

In the display panel, one side of each pixel has a length of about 283.5micrometers. In addition, the optical sheet includes the prism patternshaving a pitch of about 169 micrometers and the prism patterns arearranged inclined with respect to the sub-pixels at an angle of about 28degrees. The diffusion patterns are arranged on the prism patterns.

FIG. 5A shows the display panel that displays the image to which thewhite pattern is applied and FIG. 5B shows the display panel thatdisplays the image to which the dot pattern is applied. FIG. 5C showsthe display panel that displays the image to which the vertical linepattern is applied and FIG. 5D shows the display panel that displays theimage to which the horizontal line pattern is applied.

As shown in FIG. 5A to 5D, the optical sheet on which the patternpatterns are arranged weakens the periodicity of the brightness, whichis periodically changed in the display panel, thereby decreasing themoiré effect.

FIG. 6 is a sectional view showing another embodiment of an opticalsheet of FIG. 1. In FIG. 6, the same reference numerals denote the sameelements in FIG. 2, and thus detailed description of the same elementswill be omitted.

Referring to FIG. 6, an optical sheet 340 includes a base sheet 345,peaks 350 and valleys 360 formed on a first surface of the base sheet345, diffusion patterns 370 arranged on the peaks 350 and valleys 360,and reflection patterns 390 arranged on a second surface of the basesheet 345, which faces the first surface.

The reflection patterns 390 may be attached onto the base sheet 345 byusing adhesive or a pressure-sensitive adhesive. The reflection patterns390 include a material that reflects the light, such as titanium oxide(TiOx) deposited on acrylate resin.

The reflection patterns 390 reflect the light incident through thevalleys 360 to introduce the light to be re-incident into the peaks 350,so that the brightness of the light exiting from the optical sheet 340may be improved.

FIGS. 7A, 7B, 8, and 9 are views illustrating a method of manufacturingan optical sheet of FIG. 1, in accordance with one or more embodiments.

Referring to FIG. 7A, first, a transparent polymer material is pressedout to form a thin base sheet 345.

Then, a roller 550 is applied to the base sheet 345. The roller 550includes a metallic material, and the roller 550 includes apressurization portion 560 and a decompression portion 570 formed on anouter surface of the roller 550. In addition, first recesses 567 (seeFIG. 7B) are formed at the pressurization portion 560 and secondrecesses 565 are formed at the decompression portion 570. The firstrecesses 567 and the second recesses 565 may be formed by processingportions of the roller 550 using a laser. Moreover, descriptions ofintervals between the first recesses 567 and intervals between thesecond recesses 565 refer to the descriptions of the diffusion patternsin FIG. 3.

Roller 550 may be applied so that the base sheet 345 is pressurized bythe roller 550, so that the peaks 350, the valleys 360, and thediffusion patterns 370 formed at the peaks 350 and the valleys 360 areformed as shown in FIG. 8. The peaks 350 are formed by the decompressionportion 570 and the valleys 360 are formed by the pressurization portion560.

The diffusion patterns 370 are outwardly protruded from the base sheet345 by the first recesses 567 and the second recesses 565. The diffusionpatterns 370 each may have a shape defining a portion of a sphericalshape or a portion of an oval shape when viewed in a sectional viewtaken along a direction orthogonal to a direction in which the peaks 350and the valleys 360 extend.

Referring to FIGS. 8 and 9, the base sheet 345, the peaks 350, thevalleys 360, and the diffusion patterns 370 are irradiated byultraviolet rays and cured, thereby forming the optical sheet 340.Descriptions of intervals between the peaks 350 and between adjacentpeaks and valleys refer to the descriptions of the diffusion patterns inFIG. 3.

The reflection patterns 390 including titanium oxide (TiOx) and acrylateresin are attached to the base sheet 345 by using an adhesive or apressure sensitive adhesive. According to the above, the diffusionpatterns of the optical sheet overlap the pixels of the display panel tochange the brightness of the light, so that the periodicity of thebrightness pattern is weakened and the moiré patterns may be reduced.

In addition, the base sheet is pressed by the roller on which are therecesses to form the diffusion patterns, so that the diffusion patternsmay be easily formed.

Although exemplary embodiments of the present invention have beendescribed, it is understood that the present invention should not belimited to these embodiments but various changes and modifications canbe made by one of ordinary skill in the art within the spirit and scopeof the present invention as hereinafter claimed.

1. A display apparatus comprising: a display panel including a pluralityof gate lines, a plurality of data lines crossing the gate lines in aplan view of the display apparatus, and a plurality of pixels defined bythe gate lines and the data lines; and a backlight unit disposed at arear portion of the display panel to supply light to the display panel,wherein the backlight unit comprises: a light source generating thelight; and an optical sheet including: a plurality of prism patternshaving a plurality of peaks and a plurality of valleys, which are formedon a first surface of the optical sheet facing the display panel, afirst plurality of diffusion patterns disposed at the plurality ofpeaks, and a second plurality of diffusion patterns disposed at theplurality of valleys, wherein the first plurality of diffusion patternsand the second plurality of diffusion patterns overlap the plurality ofpixels, and wherein the first plurality of diffusion patterns isdisposed closer to the display panel than the second plurality ofdiffusion patterns.
 2. The display apparatus of claim 1, wherein each ofthe pixels comprises a red sub-pixel, a green sub-pixel, and a bluesub-pixel, and the red, green, and blue sub-pixels extend in a firstdirection and are arranged along a second direction substantiallyperpendicular to the first direction.
 3. The display apparatus of claim2, wherein each of the red, green, and blue sub-pixels overlaps at leastone diffusion pattern of the first plurality of diffusion patterns andat least one diffusion pattern of the second plurality of diffusionpatterns.
 4. The display apparatus of claim 1, wherein the prismpatterns are arranged at a predetermined angle of inclination withrespect to at least one of the plurality of the gate lines and theplurality of data lines.
 5. The display apparatus of claim 4, whereinthe angle of inclination with respect to the plurality of gate lines isfrom about 23 degrees to about 30 degrees.
 6. The display apparatus ofclaim 5, wherein the angle of inclination with respect to the pluralityof gate lines is about 28 degrees.
 7. The display apparatus of claim 4,wherein the first plurality of diffusion patterns and the secondplurality of diffusion patterns form a set of diffusion patterns, andeach diffusion pattern of the set of diffusion patterns is spaced apartfrom an adjacent diffusion pattern of the set of diffusion patterns byan interval of P/(2 cos θ), P denoting a pitch of the plurality of prismpatterns, θ denoting the angle of inclination, θ being not equal to 90degrees and not equal to 270 degrees.
 8. The display apparatus of claim4, wherein the plurality of pixels includes a plurality of sub-pixels;each diffusion pattern of the first plurality of diffusion patterns isspaced apart from an adjacent diffusion pattern of the first pluralityof diffusion patterns by an interval of X/cos θ, X denoting a distancebetween two centerlines of two adjacent sub-pixels of the plurality ofsub-pixels, θ denoting the angle of inclination, θ being not equal to 90degrees and not equal to 270 degrees.
 9. The display apparatus of claim1, wherein each diffusion pattern of the first plurality of diffusionpatterns has a diameter of about 5 micrometers to about 50 micrometers.10. The display apparatus of claim 9, wherein the prism patterns have apitch of about 100 micrometers to about 300 micrometers.
 11. The displayapparatus of claim 1, wherein the first plurality of diffusion patternsand the second plurality of diffusion patterns form a set of diffusionpatterns, and each diffusion pattern of the set of diffusion patternsprotrudes toward the display panel and has a shape defining a portion ofa spherical shape or a portion of an oval shape when viewed in across-sectional view taken along a direction orthogonal to a directionin which the plurality of peaks and the plurality of valleys extend. 12.The display apparatus of claim 1, further comprising a light guide platedisposed adjacent to the light source and adapted to guide the lightfrom the light source to the optical sheet.
 13. The display apparatus ofclaim 1, wherein the optical sheet further comprises a reflectionpattern disposed on a second surface facing the first surface to reflectthe light.
 14. A method of manufacturing an optical sheet, the methodcomprising: preparing a base sheet; applying a roller to a first surfaceof the base sheet, the roller including: a plurality of pressurizationportions protruding from an outer surface of the roller, a firstplurality of recesses disposed at the plurality of pressurizingportions, a plurality of decompression portions disposed on the outersurface of the roller, and a second plurality of recesses disposed atthe plurality of decompression portions; pressing the first surface ofthe base sheet using the roller; forming, using the roller, a pluralityof peaks and a plurality of valleys on the first surface of the basesheet; forming diffusion patterns at the plurality of peaks and theplurality of valleys, wherein a diffusion pattern of the diffusionpatterns is formed at a valley of the plurality of valleys; and curingthe base sheet.
 15. The method of claim 14, wherein the diffusionpatterns are formed according to a predetermined interval.
 16. Themethod of claim 14, wherein the first plurality of recesses and thesecond plurality of recesses are formed by using a laser.
 17. The methodof claim 14, wherein the base sheet is cured by ultraviolet rays. 18.The method of claim 14, further comprising forming a reflection patternon a second surface opposite to the first surface.
 19. The method ofclaim 14, wherein the diffusion patterns include a first plurality ofdiffusion patterns disposed at the plurality of peaks, and the diffusionpatterns further include a second plurality of diffusion patternsdisposed at the plurality of valleys.
 20. The Method of claim 19,wherein each diffusion pattern of the first plurality of diffusionpatterns has a diameter that is greater than or equal to about 5micrometers and is less than or equal to about 50 micrometers.